The method used in making tunnels or apertures in the rock is one in which holes are drilled in the rock to be blasted in accordance with a predefined drilling pattern so that when the explosives are inserted in the holes blast, a block of a desired depth and direction is detached from the rock. The direction and the position of the holes are important when the rock is to be broken in exactly the desired manner and in sufficiently small blocks. A problem here is that when, for example, the direction of the tunnel changes or when the conditions change otherwise, `cuts` with different blasting depths, or advance lengths, are used. For each cut of a different length, a different drilling pattern is used to achieve the desired final result. For example, when automatic drilling equipment is used, a separate drilling pattern is used for each normal cut depth, and so the equipment must have much more storage capacity, which requires a complicated structure. Further, it is also frustrating to the designer and the user of the equipment that many drilling patterns are so close to one another.
The object of the invention is to provide a method by which the drawbacks of the previously known, presently used method are avoided, and an appropriate drilling operation can be conducted in a simple and easy manner in accordance with the cut length. The method of the invention is characterized in that when the drilling depth needed for the blasting differs from said predetermined blasting depth, the drilling length in the drilling pattern is changed by transferring the position of the pattern in the longitudinal direction of the tunnel in accordance with the change in the blasting depth so that the positions of the end points of the holes in said three-dimensional coordinate system are transferred by said length but remain essentially the same in respect of one another, and that said collaring surface, where the collaring points of the holes are defined, is maintained the same so that the distance between the end points of the holes and said collaring surface in the longitudinal direction of the tunnel changes by the change in said blasting length.
The essential idea of the invention is that a drilling pattern is defined for a tunnel with a cross-section of a certain type and size, the drilling pattern defining the starting point of each hole in the collaring surface, or usually level, which is crosswise of the tunnel and is defined for the collaring, and the direction and length of each hole and thereby the end point of each hole. Another essential idea of the invention is that when the drilling depth, or cut length, changes so that it is shorter or longer than the normal full blasting length, the position of the drilling pattern is transferred forward or backward from the original position in the longitudinal direction of the tunnel so that the mutual relations between the end points of the holes do not change but settle in accordance with the desired cut length in relation to the rock. Yet another essential idea is that the position of the collaring surface is maintained the same, but a new starting position is calculated for each hole in the collaring surface, or the direction from the collaring surface to the end point is maintained in accordance with the original drilling pattern.
It is an advantage of the invention that in the drilling of a tunnel or the like that has a certain shape, a single drilling pattern can be used in which the positions of all the holes in relation to one another are defined three-dimensionally. Further, when the cut length shortens or lengthens, the position of the drilling pattern is transferred from the position corresponding to the cut length, i.e. from the starting position, in the main drilling direction, i.e. toward the end of the drill holes, or in the opposite direction, simultaneously as the equipment automatically calculates, for each hole, a new starting point or direction from the collaring surface to the end points corresponding to the position of the transferred drilling pattern so that the position of that part of each hole which is to be drilled remains essentially in accordance with the original drilling pattern in relation to the other holes. The drilling pattern can thus be steplessly transformed to correspond to the desired cut length without separate drilling patterns dependent on the cut length. This simplifies the driller's work and the automatic drilling.